Latching mechanism for telescoping members



Aug. 30, 1966 J. DE LlGT 3,

LATCHING MECHANISM FOR TELESCOPING MEMBERS Filed Nov. 27, 1964 I 5 Sheets-Sheet 1 I VE N TOR. /0///v 042/47" M 2 {h ZTTOEEEYS Aug. 30, 1966 .1. DE LlGT LATCHING MECHANISM FOR TELESCOPING MEMBERS 7 Filed Nov. 27, 1964 5 Sheets-Sheet 2 INVENTOR. /0A /1/ 5J1 /7 M M, W $44 m A ORNEYS Aug. 30, 1966 J. DE LIGT 3,269,561

LATCHING MECHANISM FOR 'I'ELESCOPING MEMBERS Filed Nov. 27, 1964 5 Sheets-Sheet 5 INVENTOR. /0 //v @[Z/ f Aug. 30, 1966 J. DE LIGT LATCHING MECHANISM FOR TELESCOP ING MEMBERS Filed Nov. 27, 1964 5 Sheets-Sheet 4.

INVENTOR. 4/0/771/ @45 4/4 7- M I ATT RNEYS Aug. 30, 1966 J. DE LIGT 3,269,551

LATCHING MECHANISM FOR TELESCOPING MEMBERS Filed Nov. 27, 1964 5 Sheets-Sheet 5 ATTORNEYS United States Patent 3,269,561 LATCHING MECHANISM FOR TELESCOPING MEMBERS John De Ligt, Mnskegon, Micl1., assignor, by mesne assignments, to Dresser Industries, Inc., Dallas, Tex., a corporation of Delaware Filed Nov. 27, 1964, Ser. No. 414,109 14 Claims. (Cl. 212-128) This invention relates to improvements in latching mechanism for telescoping members, and more particularly to mechanism automatically operable to supportably connect adjacent relatively movable pieces, and then transfer the connection from one of said pieces or members to a third member, the invention being highly desirable for use in stacker cranes having a mast comprising telescopic sections, although the invention could be used on extension ladders as well as for many other purposes as will be apparent to one skilled in the art.

By way of convenience, therefore, and not by way of limitation the instant invention is herein set forth and described in association with a stacker crane having a telescopic mast of the general character of that set forth in Valliere et al. US. Letters Patent No. 3,144,137, issued August 11, 1964.

Stacker cranes usually comprise a fixed mast section depending from a superstructure, an intermediate mast section telescopically associated with the fixed section, and a bottom load carrying section telescopically associated with the intermediate section. In some instances more than one intermediate section may be desirable, but most commonly there is only a single intermediate section. It is desirable to have the intermediate section rise along with the lower load carrying section until the intermediate section reaches a predetermined height so that the stacker crane may readily pass over obstacles on the floor or ground, there being nothing extending below the load bearing section. In the past, it has been necessary to counterweight the intermediate mast section or else to drive it by suitable mechanism in order to raise it along with the load bearing section. Such counterweight or driving equipment, however, was objectionably costly and space consuming.

The instant invention has been designed to eliminate any need for counterweighting mechanism, driving means, or the like, and still provide means whereby the intermediate section of a telescopic mast may be elevated out of the way of floor obstructions along with the elevation of the load bearing section of the mast.

An important object of this invention is the provision of a simple form of mechanism which effectively establishes supporting connection between the intermediate of three adjacent members and one adjacent member, and at a predetermined location transfers the supporting connection to the other adjacent member.

It is also an important object of this invention to provide a simple form of latching mechanism for use with three adjacent members at least two of which are movable relatively to the third, and which automatically establishes a supporting connection between the intermediate member and one of the other members for joint motion therewith relatively to the third member, and automatically release that connection and establish a supporting connection between the intermediate member and the third member, permitting the first connected member to travel on relatively to the intermediate member, which mechanism automatically operates in the reverse order upon the return movement of the first connected member.

Also an object of this invention is the provision of a simple form of latching mechanism operating in general on the escapement principle, and arranged to establish supporting connection between a member carrying the 3,269,561 Patented August 30, 1966 latching means and another member on one side thereof, and at a predetermined location transfer the engagement to a member on the opposite side of the latch carrying member.

Still a further important object of this invention is to provide a form of mechanism as mentioned above that is completely mechanical in operation.

Another desideratum of the instant invention is the provision of automatically operable means for use with a stacker crane having a telescopic mast including a fixed upper section, an intermediate section, and a lower load bearing section, whereby the intermediate section is moved upwardly along with and supported by the load bearing section for a predetermined distance when the intermediate section is automatically anchored to the fixed section permitting the load bearing section to continue its movement relatively to the intermediate section.

Still a further object of the invention is the provision of simple mechanical means whereby in the event the intermediate section should lose its supporting connection for any reason braking by an automatic brake supports the intermediate section.

Still a further object of the invention resides in the provision of a stacker crane provided with a telescopic mast equipped with both latching mechanism for supportably connecting sections of the mast, and braking mechanism, these mechanisms cooperating with each other in a manner such that should there be a free fall, as might be caused by a broken hoisting rope the latching mechanism will function to release itself from engagement with both the falling sections, and automatically actuate the brake mechanism to check the fall on the upper of the sections.

While some of the more salient features, characteristics and advantages of the instant invention have been above pointed out, others will become apparent from the following disclosures, taken in conjunction with the accompanying drawings, in which:

FIGURE 1 is a fragmentary side elevational view of a stacker crane equipped with mechanism embodying principles of the instant invention;

FIGURE 2 is a plan sectional view taken substantially as indicated :by the line II-II of FIGURE 1, looking in the direction of the arrows;

FIGURE 3 is a fragmentary perspective view, with parts broken away to illustrate parts therebeneath and pro:

viding a detailed showing of the mechanism embodying principles of the instant invention;

FIGURES 4, 5 and 6 are fragmentary diagrammatic showings of the latching means in different positions;

FIGURE 7 is a fragmentary perspective view with parts broken away and parts shown in section, with the mast sections in a higher position than seen in FIGURE 3 and indicating the operation of the latch mechanism;

FIGURE 8 is a view similar in character to FIGURE 7 with the mast sections at a still higher level;

FIGURE 9 is a fragmentary view similar to FIGURE 7 showing the mast sections at a still higher level; and

FIGURE 10 is another fragmentary perspective view illustrating the condition of the latch mechanism after the load bearing mast section has reached its highest position.

As shown on the drawings:

With reference more particularly to FIGURES 1 and 2, it will be seen that the stacker crane arbitrarily selected for illustration with the instant invention embodies a trolley 1 which may travel on wheels 22. riding on suitable rails 33 suitably supported on the walls of the space in which the stacker crane is to operate. The trolley 1 may function as a bridge, if no travelling bridge is provided, it being understood that in some cases there will be a travelling bridge which will be traversed by the 3 trolley, as shown in the aforesaid U.S. Letters Patent. Depending from rotating mechanism diagrammatically shown at 4 and carried by the trolley is a telescopic mast.

In the illustrated instance, the telescopic mast embodies three sections, namely a fixed section 5 depending from the rotating mechanism 4, an intermediate section 6 movable relatively to the fixed section, and a load carrying section 7 movable relatively to both the intermediate section and the fixed section.

On each of opposite sides of the fixed section 5 a longitudinally extending guide bar 8 is secured which functions as a track for a pair of rolls 99 carried by the intermediate section 6. Such arrangement keeps the parts in properly oriented positions when operating. Similarly, on each of opposite sides of the intermediate section a guide bar 10 is provided which is contacted by rolls 11 carried by the load bearing section 7: The sections are elevated by means of a rope 12 reeved around sheaves 13 secured to the load bearing section 7. The rope extends upwardly inside the respective mast sections and is anchored to a rope drum 14 driven by an electrical motor 15 or the equivalent, both of which are carried by the aforesaid trolley 1. When the drum is rotated in one direction, sections 6 and 7 are elevated, and when the rope travels in the opposite direction the sections descend by gravity.

The load bearing section 7 is provided in the illustrated instance with outwardly extending carrying forks 16 whereby the load is maintained clear of the mast at all times during operation.

An operators cab, not shown in the drawings, is mounted on the intermediate section in any suitable manner such as illustrated in the aforesaid U.S. Letters Patent, and the flying sheave 17, seen in FIGURE 3, is for electric cable means leading to the operators cab.

The latching mechanism which supportably connects the section 6 and section 7 so that the former can be carried upwardly by the latter, and which then releases such connection and establishes a supporting connection between section 5 and section 6 so the latter can be supported from the former, is shown on one side of the mast structure, a side carrying the guide bars 8 and 10 on sections 5 and 6 respectively. While one such form of mechanism is illustrated in the drawings, it will be understood that should load conditions indicate, a like latching assembly could be incorporated on the opposite side of the structure as well. Likewise, while only one mechanical brake is shown, it is obvious that another mechanical brake associated with other latching apparatus could be included on the opposite side of the structure as well.

With reference now to FIGURES 3 and 4, it will be noted that welded or equivalently secured to the inside face of the load bearing section 7 is a fiat bar cam, generally indicated by numeral 18 having an upper straight portion 19, an intermediate diagonal portion 20, and a lower straight portion 21. Spaced a short distance from the bar cam 18 is a post cam also secured to the inside face of section 7, and generally indicated by numeral 22. This post cam has a flat top 23 and a bevel portion 24 at the lower end thereof sloping outwardly and downwardly toward the wall of section 7. Directly above the cams 18 and 22, are a pair of like earns 25 and 26 respectively secured to the outer face of the fixed mast section 5 and in this instance the bevel portion of the post cam 26 will slope downwardly and inwardly toward the wall of section 5. These cams, in a manner to be later described, effect the actuation of the latch mechanism.

The latching mechanism is mounted on the wall of the intermediate mast section 6 by means of an upper pair of blocks 27 and a lower pair of blocks 28 spaced therefrom, all of which are identical and secured rigidly to the wall of section 6. As seen best in FIGURE 3, a pair of spaced rods are held in the blocks 27 and 28 at their ends forming a rigid structure. A latch body casting 30 which in effect forms a rectangular frame,

is provided with corner bosses 31 engaged around the rods 2929 so that this casting may slide up and down the rods. Compression springs 3232, one disposed around each of the rods 29-29 between the respective upper block 27 and the body casting constantly urge the body casting 30 downwardly. However, in the usual operation of the crane, the body casting 30 is held in the position seen in FIGURE 3 above the lower blocks 28 by pressure on the latching mechanism caused by the cam 22 on the mast section 7 or by the cam'26 on the mast section 5, as the case may be.

A latch 33 mounted to pivot on a crosspin 34 is disposed in the open center of the body casting 30, and can rock backward and forward through that opening as well as through an opening 35 in the wall of the intermediate mast section 6 so as to find engagement with the cam 26 on the upper fixed mast sec-tion 5. The opening 35 in the section wall is at least as large as the open center of the body casting, and near the top thereof the opening 35 is extended laterally in the form of an elongated slot 136. The free end of the latch is provided with detent means in the form of transverse grooves 36 and 37 on opposite sides of the latch. The latch also has a pair of side plates 38-38 securely fixed :to the latch and projecting beyond the latch in each direction. These side plates also pivot with the latch on the pin 34 and the side plates carry cam riding rollers 39 and 40 in the end portions thereof.

To maintain the latch with the roller 39 resting upon the top of the lowerpost cam 22 as seen in FIGURES 3 and 7, and prevent the latch from pivoting counterclockwise, a lock bar 41 is seated in the groove or detent means 37 of the latch. The lock bar is held by a slide plate 42, which is slid-able on a pin 43 fixedly secured to the body casting 30. Projecting outwardly from one side of the slide 42 is a pair of spaced pins 44, and a similar pair of spaced pins 45 project inwardly from the opposite side of the slide. The aforesaid bar cams 18 and 25 engage between the pins 44 and 45 respectively in order to engage and disengage the locking bolt 41 with or from the latch, as the case may be.

For engagement of the pins 45 by the cam 25, it will be noted that the pins 45 extend through the aforesaid slot 136 in the wall of the intermediate section 6, as seen best in FIGURE 3.

In operation, the latch mechanism is completely mechanioal and automatic and responds easily to normal up and down movements of sections 6 and 7 of the mast to release supporting engagement between the intermediate section and one of the other two sections and transfer that supporting engagement between the intermediate section and the third section. In FIGURES 4 to 10 inclusive the apparatus is shown in different stages of operation, and in describing this operation, it must be assumed that the mast is to be gradually elevated to its highest point from the normally lowered condition of the mast as seen in FIGURE 3.

As the mast is seen in FIGURE 3, the intermediate mast section 6 is supported on the lower load bearing section 7 by virtue of the roller 39 on the latch 33 seating on the upper flat face of the post cam 22 on the load bearing section. The latch is prevented from turning by reason of the latching bolt 41 being seated in groove 37 of the latch. As the load bearing section 7 is elevated there will be a tendency to compress the springs 32-32 and such compression of the springs is limited by a stop block 46 firmly secured to the wall of the intermediate section 6.

The intermediate section 6 will be carried. upward along with the lower section 7 until the latch is engaged wlth the upper end of the post cam 26 on the upper fixed section 5. During this movement the roller 40 on the latch will first contact the lower bevel portion of the cam 26 and contemporaneously therewith the lower straight portion of cam 25 will enter between the pins 45 on the slide 42, as seen in FIGURE 7. As this movement continues to the point where the roller 40 rides up above the bevel portion of cam 26 on its straight side wall, the latch will be forced slightly clockwise, as seen in FIGURE 6, to thereby relieve pressure of the latch on the latching bolt 41. The intermediate section, however, continues to be fully supported by virtue of the roll 39 still resting upon the cam 22 and the roll 40 riding the face of the cam 26. Immediately upon the relief of pressure on the latching bolt, the bolt is withdrawn by virtue of the oblique portion of cam 25 moving the slide 42 outwardly to the position seen in FIGURE 8. While this occurs there will be an instant when the intermediate section is supported as seen in FIGURE 5 with the rolls 39 and 40 resting on the flat tops of cams 22 and 26 respectively. As the cam 22 continues upwardly the latch turns counterclockwise and the roll 39 follows the inner face of cam 22 while the roll 40 seats on top of the cam 26 as seen in FIGURE 4, and at the same time the cam 18 enters between the pins 44 on the slide 42 and the oblique portion 20 of this cam moves the slide 42 to the right as seen in FIGURE 8 to the position of FIGURE 9 with the latching bolt 41 now engaged in the groove 36 of the latch, and the intermediate section 6 is now firmly supported by the fixed top section 5 of the mast, and the load bearing section is free of engagement with the latch to pass freely on thereby.

As seen in FIGURE 10, supporting engagement is established by the latch between the fixed section 5 and the intermediate section 6, while the load bearing section has passed upwardly beyond that engagement. The transfer of the latch engagement between sections 7 and 6 to a supporting engagement :between sections 5 and 6 is a smooth flowing automatic operation whether the load is being elevated extremely slowly or fairly rapidly.

When the load bearing section 7 moves downwardly, the latch mechanism is actuated reversely to the above described manner. The post cam 22 will move the latch suificiently to relieve pressure on the latching bolt 41, the bolt will be withdrawn by the bar cam 18, the post cam 26 will effect rocking of the latch to the position of FIGURE 7, and the bar cam 25 will move the latching bolt into holding position.

Braking means to stop any unintentional descent of the intermediate mast section 6 are carried by this mast section adjacent the upper end thereof. These braking means, as best seen in FIGURE 3, are carried by a mounting plate 47 secured over a suitable opening in the wall of the section 6 in front of the guide bar 8 on the fixed section 5. The braking mechanism per se is more fully set forth and described, as well as claimed, in my copending application entitled, Safety B-rake, Serial No. 352,536, filed March 17, 1964. Therefore, it will sufiice to state herein that the braking means embody a pair of downwardly pivotal cams 48-48, each of which has a portion abutting a pin 49 carried on one end of a brake arm 50 pivoted to the opposite face of the mounting plate as indicated at 51, and which brake arm carries a brake shoe 52 thereon for engagement with the guide bar 8. A spring 53 urges the arms and brake shoes into braking engagement with the guide bar 8. The braking mechanism is shown in disengaged position in FIGURE 3 and the braking shoes are maintained in disengaged position by means of a striker plate 54 on the upper portion of a rod 55 slidable through suitable angle guides 56 secured .to the section wall. A reinforced cross-link 57 connects the rod 55 to another rod 58 which extends through an aperture in the aforesaid stop block 46 on top of the latch assembly body casting. A linkage is thereby formed and when the sections 6 and 7 are supportably connected by the latch, the upward pressure on the body casting 30, compressing the springs 3232, also urges the striker plate 54 into engagement with the inner ends of the cams 48'-48, preventing these cams from pivoting, and holding the braking means in disengaged position. The brake shoes cannot move to braking position as long as the striker plate prevents pivotal movement of the cams.

If, for any reason, such as false support of the intermediate section 6 by a building obstruction, racks being serviced, or the like, that section will be effectively supported by the brake mechanism which is released to be forced into braking position by the spring 53, because when the lower section 7 moves away from the latching mechanism, the latch means will be pushed downwardly on the post 2929 by the springs 3%32 letting the striker plate 54 drop away from the brake actuating cams. Additional support for the intermediate section in its lowermost position is provide-d by stop blocks 59 and 60, .the lower block 59 being fixedly secured to the wall of the fixed mast section 5 and the upper stop block 60 being secured to the inside face of the wall of the intermediate section -6. The braking mechanism effectively prevents any undue jar on the stop blocks if and when they meet.

The control of .the braking means by way of the latching assembly provides other distinct advantages. For example, should the hoisting rope break when the intermediate m-ast section is being supported by the load bearing section 7, .both these sections will start a free fall together. However, the springs 3232 having been previously compressed, now effect a separation between the lower section 7 and the intermediate section 6 by forcing down the latch assembly, and this effective separation is sufiicient to release the braking mechanism and permit it to move to bra-king position. And the intermediate mast section 6 becomes locked to the fixed section 5 by way of the braking means. Thus, the crane operator riding in the cab attached to the intermediate section 6 is given full protection. Even in extreme falls, the braking means will slow down the intermediate section 6, if it is not fully stopped sooner, until the stop blocks 59 and 60 engage and that engagement will not be of such suddenness or force as to injure the operator. The load bearing section is permitted to fall free since there is no known braking system that would effectively stop the loaded section, and any attempt to stop the loaded section not only exposes the operator to danger but also will frequently-result in extensive damage to the main crane structure.

From the foregoing, it is apparent that I have provided novel latching means which provides a complete and simple mechanical means for positioning mast sections so they do not project fully extended below the load bearing section, and utmost clearance is provided at all times. This is accomplished in the instant case with the elimination of counterweighting the intermediate mast section, elaborate rope reeving arrangements, separate driving means for the intermediate section, and other equivalent expensive and space consuming arrangements. The latching assembly and the actuating cams therefor may be positioned at any desired elevation on the mast sections, so they can have any required or relative position, depending upon the purpose the crane is desired to accomplish. It will also be noted that the combination wherein the braking means are controlled by the latch assembly provides additional safety advantages.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

I claim as my invention:

1. In load lifting apparatus having three adjacent members, two of which members are movable relatively to each other and to the third member, supporting means comprising movable holding means carried by the intermediate of the three members engageable with a second of said members on one side thereof to be supported thereby, and

cam means carried by said second member to automatically move said holding means into engagement with the third of said members to be supported thereby when said second member has moved a predetermined distance relatively to the third member in one direction. 2. In load lifting apparatus having three adjacent members, two of which members are movable relatively to each other and to the third member, supporting means comprising movable holding means carried by the intermediate of the three members engageable with a second of said members on one side thereof to be supported thereby,

cam means carried by said second member to automatically move said holding means into engagement with the third of said members to be supported thereby when said second member has moved a predetermined distance relatively to the third member in one direction, and

cam means on the third member to move said holding means into supporting engagement with the second member to return the support of the immediate member thereto when the second member has moved a predetermined distance in the reverse direction.

3. In load lifting apparatus having three adjacent members, two of which members are movable relatively to each other and to the third member, supporting means comprising movable holding means carried by the intermediate of the three members engageable with a second of said members on one side thereof to be supported thereby, and

cam means carried by said second member to automatically move said holding means into engagement with the third of said members to be supported thereby when said second member has moved a predetermined distance relatively to the third member in one direction,

movable locking means also carried by the intermediate section to retain said holding means in holding position, and

means on both the second and third sections to respectively release and reset said locking means in timed relationship with the movement of said holding means. 4. Load lifting apparatus comprising in combination, three adjacent upright members including an intermediate member and a member on each side thereof,

one of the side members being fixed and the other members being movable relatively thereto and to each other,

holding means carried by the intermediate member movable from engagement with and support by one side member to engagement with and support by the other side member, and

cam means carried by both said side members to move said holding means and change the engagement of said holding means in accord with the direction of travel of the movable side member.

5. Load lifting apparatus comprising in combination, three adjacent upright members including an intermediate member and a member on each side thereof, one of the side members being fixed and the other members being movable relatively thereto and to each other, holding means carried by the intermediate member movable from engagement with and support by one side member to supporting engagement with and support by the other side member,

cam means carried by both said side members to move said holding means and change the engagement of said holding means in accord with the direction of travel of the movable side member,

locking means carried by said intermediate member to retain said holding means in engaged position, and

- other cam means carried by said side members to release and reset said locking means in accord with changes in engagement of said holding means.

6. Load lifting apparatus comprising in combination,

three adjacent upright members including an intermediate member and a member on each side thereof,

one of the side members being fixed and the other members being movable relatively thereto and to each other,

holding means carried by the intermediate member movable from engagement with and support by one side member to engagement with and support by the other side member,

cam means carried by both said side members to move said holding means and change the engagement of said holding means in accord with the direction of travel of the movable side member,

braking means carried by said intermediate section for engagement with a part of said fixed member, and

means controlled by said holding means to move said braking means to braking position in the event support of the intermediate member by the movable side member fails. 7. Load lifting apparatus comprising in combination, three adjacent upright members including an intermediate member and a member on each side thereof, one of the side members being fixed and the other members being movable relatively thereto and to each other,

holding means carried by the intermediate member movable from engagement with and support by one side member to engagement with and support by the other side member,

cam means carried by both said side members to move said holding means and change the engagement of said holding means in accord with the direction of travel of the movable side member,

braking means carried by said intermediate section for engagement with a part of said fixed member,

resilient means biasing said braking means braking position, and

a linkage connecting said holding means and said braking means to retain the letter in non-braking position against the action of said resilient means as long as the holding means are in supporting engagement with either side member and to release said braking means if such engagement fails.

8. Load lifting apparatus comprising in combination,

three adjacent upright members including an intermediate member and a member on each side thereof,

one of the side members being fixed and the other members being movable relatively thereto and to each other, i

a latch mounted on said intermediate member for rocking movement through an opening in the intermediate member,

means on each side of said latch for engagement with the fixed member and the movable side member respectively,

movable locking means to retain said latch means in engagement with one of said side members, and

like cam means on said side members to alternately move said locking means to released position and to reset position in timed relationship with the rocking of said latch dependent on the direction of movement of the movable side member.

9. Load lifting apparatus comprising in combination,

three adjacent upright members including an intermediate member and a member on each side thereof,

one of the side members being fixed and the other members being movable relatively thereto and to each other,

a latch mounted on said intermediate member for rocking movement through an opening in the intermediate member,

means on each side of said latch for engagement with the fixed member and the movable side member respectively,

movable locking means to retain said latch means in engagement with one of said side members,

like cam means on said side members to alternately move said locking means to release position and to reset position in timed relationship with the rocking of said latch dependent on the direction of movement of the movable side member,

braking means for braking engagement with a part of said fixed member,

a body on said intermediate section carrying said latch and movable relatively to said intermediate section when the engagement of said latch means with either side member fails, and

means connecting said body and said braking mechanism whereby a movement of said body controls the action of said braking means.

10. In a stacker crane,

a superstructure,

a telescopic mast depending from said superstructure and including a fixed section, an intermediate movable section and a movable load bearing section,

latch means carried by said intermediate section movable into engagement with either of the fixed or load bearing sections to be supported thereby, and

actuating means carried by both the fixed and load bearing sections to actuate said latch means to change the engagement thereof with either of said fixed or load bearing sections from one to the other depending on the direction of travel of the load bearing section.

11. In a stacker crane,

a superstructure,

a telescopic mast depending from said superstructure and including a fixed section, an intermediate movable section and a movable load bearing section,

latch means carried by said intermediate section movable into engagement with either of the fixed or load bearing sections to be supported thereby,

actuating means carried by both the fixed and load bearing sections to actuate said latch means to change the engagement thereof with either of said fixed or load bearing sections from one to the other depending on the direction of travel of the load bearing section,

a movable lock bar to engage said latch means and retain the same supportingly engaged with either the fixed or load bearing sections, and

means on said fixed and load bearing sections to release and reset said lock bar in timed relationship with a change of engagement of said latch means.

12. In a stacker crane,

a superstructure,

a telescopic mast depending from said superstructure and including a fixed section, an intermediate movable section and a movable load bearing section,

latch means carried by said intermediate section movable into engagement with either of the fixed or load bearing sections to be supported thereby,

actuating means carried by both the fixed and load bearing sections to actuate said latch means to change the engagement thereof with either of said fixed or load bearing sections from one to the other depending on the direction of travel of the load bearing section,

braking means on said intermediate section movable to engage a part of said fixed section and hold said intermediate section against a free fall, and

means associated with said latch means to move said braking means into braking position upon a failure of engagement between said latch means and either of said fixed or load bearing sections.

13. In a stacker crane,

a superstructure,

a telescopic mast depending from said superstructure and including a fixed section, an intermediate movable section and a movable load bearing section,

a pair of spaced rods secured to the intermediate section,

an open-centered body slidable on said rods,

resilient means urging said body downwardly,

a latch pivoted in said body and rockable through an opening in the wall of the intermediate section,

opposed engaging elements on said latch, one to engage the load bearing section and the other the fixed section,

a slidable lock bar carried by said body to retain said latch engaged with either the load bearing section or the fixed section,

like cam means on the fixed and load bearing sections to withdraw the lock bar, rock the latch and reset the lock bar to transfer engagement of the latch from one section to the other,

braking means carried by the intermediate section for gripping a part of the fixed section and support the intermediate section therefrom should latch engagelment fail, and

a linkage between said latch body and said braking means to apply upward pressure on the braking means when the latch is engaged with a section and hold said braking means in non-braking position.

14. In a stacker crane,

a superstructure,

a telescopic mast depending from said superstructure and including a fixed section, an intermediate movable section and a movable load bearing section,

a pair of spaced rods secured to the intermediate section,

an open-centered body slidable on said rods,

resilient means urging said body downwardly,

a latch pivoted in said body and rockable through an opening in the wall of the intermediate section to engage either the load bearing section or the fixed section,

such engagement resulting in elevating said body and latch against the action of said resilient means,

means on said fixed and load bearing sections for automatically transferring the latch engagement from one to the other as the load bearing section moves relatively to the fixed section,

braking means on said intermediate section for gripping a part of said fixed section and support the intermediate section when there is no engagement by the latch with another section, and

a linkage between said body and said braking mechanism to apply upward pressure on the braking mechanism and hold the same in non-braking position when the latch engages the fixed or load bearing section.

References Cited by the Examiner UNITED STATES PATENTS 2,502,465 4/ 1950 Lehmann 187-9 2,906,373 9/ 1959 Hastings et al 1879 3,051,265 8/ 19621 Boyajain et al 187-9 3,064,761 11/1962 Ramsey 187-9 3,144,137 8/ 1964 Valliere et a1 212128 3,187,842 6/1965 Quayle 187-9 EVON C. BLUNK, Primary Examiner.

A. H. NIELSEN, Assistant Examiner. 

1. IN LOAD LIFTING APPARATUS HAVING THREE ADJACENT MEMBERS, TWO OF WHICH MEMBERS ARE MOVABLE RELATIVELY TO EACH OTHER AND TO THE THIRD MEMBER, SUPPORTING MEANS COMPRISING MOVABLE HOLDING MEANS CARRIED BY THE INTERMEDIATE OF THE THREE MEMBERS ENGAGEABLE WITH A SECOND OF SAID MEMBERS ON ONE SIDE THEREOF TO BE SUPPORTED THEREBY, AND CAM MEANS CARRIED BY SAID SECOND MEMBER TO AUTOMATICALLY MOVE SAID HOLDING MEANS INTO ENGAGEMENT WITH THE THIRD OF SAID MEMBERS TO BE SUPPORTED THEREBY WHEN SAID SECOND MEMBER HAS MOVED A PREDETERMINED DISTANCE RELATIVELY TO THE THIRD MEMBER IN ONE DIRECTION. 